1. Cloud Types & Precipitation
Chapter 18.3
Cloud Types & Precipitation
Who is Stan Hatfield and Ken Pinzke

2. What is a cloud?
A cloud is a visible group of tiny water droplets or ice crystals in the air.
YouTube:
Strange Cloud
Formations

3. 3 CONDITIONS ARE NECESSARY FOR CLOUDS TO FORM.
The air temperature must be lowered to the dew point. (Air is saturated)
A solid surface must be available for condensation to occur. (condensation nuclei)
Low pressure

4. Clouds are classified by
form (shape)
height

5. 4 BASIC FORMS (Shapes) OF CLOUDS
Cirrus – wispy, feathery
Cumulus – piled, fluffy
Stratus – layered
Nimbus - rain

6. 3 Levels of Cloud Height
Height is determined by where the base of the cloud is
High (above 6000m)
Middle (2000m – 6000m)
Low (below 2000m)
Base

7. HIGH CLOUDS
All high altitude clouds are made of ice crystals due to the cold air in the upper sky.
Group consists of
Cirrus
Cirrostratus
Cirrocumulus

8. Cirrus Clouds

10. Cirrostratus Clouds

12. Cirrocumulus Clouds

13. Middle Clouds
Middle clouds are made of ice crystals and water droplets.
Group consists of
Altocumulus
Altostratus

14. Altocumulus

16. Altostratus

17. Low Clouds Low clouds consist of water droplets. Group consists of
Cumulus
Stratus
Stratocumulus
Nimbostratus (rain cloud)

18. Cumulus

20. Stratus

22. Stratocumulus

24. Nimbostratus

26. Cumulonimbus Clouds (Thunder Clouds)
build up from low altitudes to elevations over 6000m
associated with:
lightning & thunder
Hail
Tornadoes
heavy rain

28. Contrails

29. Cloud Classification
Makes no sense without caption in book

30. 18.3 Cloud Types and Precipitation
Fog
18.3 Cloud Types and Precipitation
 Fog is defined as a cloud with its base at the ground.
 Fog Caused by:
• As the air cools, it becomes denser and drains into low areas such as river valleys, where thick fog accumulations may occur.
• When cool air moves over warm water, enough moisture may evaporate from the water surface to produce saturation.

34. Precipitation
Any liquid or solid particle that falls from a cloud

35. What is Collision-coalescence?
Water droplets within a cloud crash into each other and get bigger and bigger until they fall from the cloud.

37. Starts as snow falling from clouds Melts on its way down
Rain
Starts as snow falling from clouds
Melts on its way down
Reaches ground as liquid
Dry air: rain drop may evaporate before hitting the ground

38. Ice falling from clouds Size & shape depend on how cold it is
Snow
Ice falling from clouds
Size & shape depend on how cold it is
Temperature must be below freezing during journey
Dry air: small crispy snowflakes
Wet air: large wet snowflakes (great for making snowballs)

40. Sleet
Ice falling from clouds
Layer of warm air melts to rain
Then refreezes again in cold air above the ground

41. Freezing Rain
Ice falling from clouds
Layer of warm air melts to rain
The ground is below freezing
Rain hits the ground and freezes on contact

43. Hail
Balls of ice that fall from a cumulonimbus cloud
Only during a thunderstorm
Ice gets swept up and down in updrafts
They grow larger as water refreezes each time they rise.

44. Largest Recorded Hailstone
Makes no sense without caption in book